In a heavy 3-quart saucepan cook bacon over medium heat until lightly browned, about 10 minutes. Do not drain fat.

Add butter or margarine and heat until melted. Stir in lettuce and saute 2 minutes. Blend in flour with a wire whisk. Stir over medium heat until well blended and evenly cooked, about 2 to 3 minutes. Remove from heat.